1. Field of the Invention
The present invention relates generally to prosthetics, and, more specifically to an attachment system used in the donning/doffing of a socket onto a residual limb. The present invention more particularly relates to an attachment system that requires little or no clearance inside the socket between the socket and the residual limb, that controls rotation of the prosthesis, and that may be used with a suction-fit socket system. The invented attachment system extends from the side of a liner on the user's limb, through an aperture in the socket, to the outer side of the socket, substantially proximal on the limb and on the socket relative to conventional more “distal” attachment devices. Therefore, the invented attachment may properly be called an exterior, proximal attachment device for a prosthesis.
2. Related Art
For years, many different methods have been used to retain or “suspend” a prosthetic limb on an amputee's residual limb. Gravitational and other forces, for example, from movement of the limbs, tend to cause separation between the prosthetic limb and the patient's residual limb during use. This happens, for example, during the swing phase of gait, when a prosthetic leg is additionally subjected to centrifugal forces. Patients have routinely worn a variety of belts, straps, cuffs, and harnesses to retain their prosthetic limbs against separation from the limb during these periods. However, such devices are often inconvenient and may tend to cause chafing against the patient's body, giving rise to sores and abrasions.
The manner in which an artificial limb is suspended and/or attached to the residual limb determines the amount of control an amputee has over the prosthesis. Therefore, by improving suspension/attachment without adding weight and excessive mechanism, the amputee may obtain improved comfort, convenience, and suspension mobility.
A common approach to tackling this problem has led to the design of a roll-on suction liner, which is rolled onto the residual limb and attached at its distal end to a socket or artificial limb. The liner, which is usually fabricated from silicone, or some other gel form, fits snugly over the residual limb, preferably completely covering the distal end of the residual limb and extending for at least several inches to cover the entire circumference of the proximal region of the residual limb. The liner, in turn, is enveloped, especially at its distal end, by the socket of the prosthesis, which is also called a “hard socket.” A suction fit is preferably formed between the hard socket and the liner. This suspension method is very advantageous for the amputee. It gives the amputee the ability to better control the prosthesis and provides for useful sensory or proprioceptive feedback. Suction suspension also makes a prosthesis feel lighter, compared to other forms of suspension. Unfortunately, only a small percentage of amputees can successfully and comfortably wear a liner without another form of suspension. Therefore, the socket liner is typically equipped with a detachable component, at its distal end, which mates with a locking device in the interior of the socket at the bottom of the interior space or “well.” This system secures the distal end of the, residual limb/liner to the distal end of the artificial limb socket well, and, hence, is called a “distal attachment.” The locking device in the distal end of the socket well typically employs a spring-loaded clutch mechanism or a pin-lock mechanism. The component on the distal end of the liner is typically a cylindrical barb-shaped structure or frictionally-retained pin.
One problem associated with such designs is the tugging or pull on the distal end of the limb. Most of these locks are not air tight, thus allowing air to flow into the hard socket and to eliminate the “suction.” When this happens, the only suspension is the pin, which is a traction suspension, rather than suction. In cases where prosthetic socks are worn outside the liner, there is a risk the user's limb will become trapped in the socket if the sock is caught in the locking device. In these incidents, most patients are forced to make emergency trips to their practitioner to remove the prosthetic. Also, the locking device and attachment component cooperate in such a way to permit the barb or pin to lock in a plurality of longitudinal positions, which affects the overall length of the prosthesis. This can make it difficult for the patient to consistently achieve the same prosthetic configuration when the residual limb and the artificial limb are articulated. It should be further noted that, by weight of the lock being added at the distal end of the residual limb or near the distal end of the socket, this can make the prosthetic device feel heavier because of a “lever arm” effect, than if the same weight were placed more proximally. Additionally, many amputees, whether because of the length of their residual limb or their height, do not have room in the suction liner-socket-prosthesis combination for a distal locking mechanism. Or, additionally, use of a distal lock may limit what other prosthetic components that patient may use.
Despite the large number of suspension options available, none of the above-mentioned devices act to eliminate rotation between the hard socket and the suction liner. In an attempt to alleviate the rotation problem, a design called a “quad socket” has been used for many years. The quad socket is shaped in a square manner more than a cylindrical manner, and forcing the “cylindrical” limb to fit tightly in this square receptacle makes the prosthesis less apt to rotate on the limb, much as if you made a wheel square. Unfortunately, this is not a very comfortable position for the limb. Today, there has been a trend toward more naturally-shaped sockets, making rotation control even more difficult.
Therefore, there is still a need for an improved attachment system for prosthetics. Also, there is a need for improving retention of the stump in the socket without sacrificing the patient's comfort and without comprising on expense, weight and simplicity of use of the prosthesis. There also is a need for improving rotation control, which will improve the patient's overall comfort and agility.